LEVEL II SCOUR ANALYSIS FOR BRIDGE 34 (ROCHTH00210034) on TOWN HIGHWAY 21, crossing the WHITE RIVER, ROCHESTER, VERMONT Open-File Report 97-670 Prepared in cooperation with VERMONT AGENCY OF TRANSPORTATION and FEDERAL HIGHWAY ADMINISTRATION U.S. Department of the Interior U.S. Geological Survey
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U.S. Department of the InteriorU.S. Geological Survey
-3
LEVEL II SCOUR ANALYSIS FORBRIDGE 34 (ROCHTH00210034) onTOWN HIGHWAY 21, crossing theWHITE RIVER,
ROCHESTER, VERMONT
By EMILY C. WILD and JAMES DEGNAN
U.S. Geological SurveyOpen-File Report 97-670
Prepared in cooperation with
VERMONT AGENCY OF TRANSPORTATION
and
FEDERAL HIGHWAY ADMINISTRATION
Pembroke, New Hampshire
1997
U.S. DEPARTMENT OF THE INTERIOR
BRUCE BABBITT, Secretary
U.S. GEOLOGICAL SURVEYMark Schaefer, Acting Director
For additional information Copies of this report may bewrite to: purchased from:
District Chief U.S. Geological SurveyU.S. Geological Survey Branch of Information Services361 Commerce Way Open-File Reports UnitPembroke, NH 03275-3718 Box 25286
Denver, CO 80225-0286
-1
CONTENTSIntroduction and Summary of Results ............................................................................................................... 1
Level II summary ............................................................................................................................................... 7Description of Bridge ................................................................................................................................... 7Description of the Geomorphic Setting........................................................................................................ 8Description of the Channel........................................................................................................................... 8Hydrology..................................................................................................................................................... 9 Calculated Discharges .......................................................................................................................... 9Description of the Water-Surface Profile Model (WSPRO) Analysis ......................................................... 10 Cross-Sections Used in WSPRO Analysis............................................................................................ 10 Data and Assumptions Used in WSPRO Model ................................................................................... 11Bridge Hydraulics Summary........................................................................................................................ 12Scour Analysis Summary ............................................................................................................................. 13 Special Conditions or Assumptions Made in Scour Analysis............................................................... 13 Scour Results......................................................................................................................................... 14Riprap Sizing................................................................................................................................................ 14
A. WSPRO input file.................................................................................................................................... 19
B. WSPRO output file .................................................................................................................................. 21
C. Bed-material particle-size distribution .................................................................................................... 28
D. Historical data form................................................................................................................................. 30
E. Level I data form...................................................................................................................................... 36
F. Scour computations.................................................................................................................................. 46
FIGURES
1. Map showing location of study area on USGS 1:24,000 scale map ............................................................. 3 2. Map showing location of study area on Vermont Agency of Transportation town
highway map ................................................................................................................................... 4 3. Structure ROCHTH00210034 viewed from upstream (July 23, 1996) ........................................................ 5 4. Downstream channel viewed from structure ROCHTH00210034 (July 23, 1996)...................................... 5 5. Upstream channel viewed from structure ROCHTH00210034 (July 23, 1996)........................................... 6 6. Structure ROCHTH00210034 viewed from downstream (July 23, 1996). ................................................. 6 7. Water-surface profiles for the 100- and 500-year discharges at structure
ROCHTH00210034 on Town Highway 21, crossing the White River, Rochester, Vermont......................................................................................................................... 15
8. Scour elevations for the 100- and 500-year discharges at structure ROCHTH00210034 on Town Highway 21, crossing the White River, Rochester, Vermont......................................................................................................................... 16
TABLES
1. Remaining footing/pile depth at abutments for the 100-year discharge at structureROCHTH00210034 on Town Highway 21, crossing the White River,Rochester, Vermont ............................................................................................................................ 17
2. Remaining footing/pile depth at abutments for the 500-year discharge at structure ROCHTH00210034 on Town Highway 21, crossing the White River,Rochester, Vermont ............................................................................................................................ 17
iii
0iv
CONVERSION FACTORS, ABBREVIATIONS, AND VERTICAL DATUM
Multiply By To obtain
Length
inch (in.) 25.4 millimeter (mm) foot (ft) 0.3048 meter (m) mile (mi) 1.609 kilometer (km)
Slope
foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)Area
square mile (mi2) 2.590 square kilometer (km2) Volume
cubic foot (ft3) 0.02832 cubic meter (m3)Velocity and Flow
foot per second (ft/s) 0.3048 meter per second (m/s)cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)cubic foot per second per 0.01093 cubic meter per square mile second per square [(ft3/s)/mi2] kilometer [(m3/s)/km2]
OTHER ABBREVIATIONS
BF bank full LWW left wingwallcfs cubic feet per second MC main channelD50 median diameter of bed material RAB right abutmentDS downstream RABUT face of right abutmentelev. elevation RB right bankf/p flood plain ROB right overbankft2 square feet RWW right wingwallft/ft feet per foot TH town highwayJCT junction UB under bridgeLAB left abutment US upstreamLABUT face of left abutment USGS United States Geological SurveyLB left bank VTAOT Vermont Agency of TransportationLOB left overbank WSPRO water-surface profile model
In this report, the words “right” and “left” refer to directions that would be reported by an observer facing downstream.
Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929-- a geodetic datum derived from a general adjustment of the first-order level nets of the United States and Canada, formerly called Sea Level Datum of 1929.
In the appendices, the above abbreviations may be combined. For example, USLB would represent upstream left bank.
LEVEL II SCOUR ANALYSIS FOR BRIDGE 34 (ROCHTH00210034) ON TOWN HIGHWAY 21,
CROSSING THE WHITE RIVER, ROCHESTER, VERMONT
By Emily C. Wild and James Degnan
INTRODUCTION AND SUMMARY OF RESULTS
This report provides the results of a detailed Level II analysis of scour potential at structure ROCHTH00210034 on Town Highway 21 crossing the White River, Rochester, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, obtained from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D.
The site is in the Green Mountain section of the New England physiographic province in central Vermont. The 74.8-mi2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is suburban on the upstream and downstream left overbanks, though brush prevails along the immediate banks. On the upstream and downstream right overbanks, the surface cover is pasture with brush and trees along the immediate banks.
In the study area, the White River has an incised, straight channel with a slope of approximately 0.002 ft/ft, an average channel top width of 102 ft and an average bank height of 5 ft. The channel bed material ranges from sand to cobble with a median grain size (D50) of 74.4 mm (0.244 ft). The geomorphic assessment at the time of the Level I and Level II site visit on July 23, 1996, indicated that the reach was stable.
The Town Highway 21 crossing of the White River is a 72-ft-long, two-lane bridge consisting of 70-foot steel stringer span (Vermont Agency of Transportation, written communication, March 22, 1995). The opening length of the structure parallel to the bridge face is 67.0 ft. The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 15 degrees to the opening while the opening-skew-to-roadway is zero degrees.
1
Channel scour, 1.5 ft deeper than the mean thalweg depth was observed along the left abutment and wingwalls during the Level I assessment. Scour countermeasures at the site includes type-1 stone fill (less than 12 inches diameter) along the upstream left bank and the upstream and downstream left road embankments, type-2 (less than 36 inches diameter) along the upstream end of the upstream left wingwall and downstream left bank, and type-3 (less than 48 inches diameter) along the downstream end of the downstream left wingwall. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E.
Scour depths and recommended rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1995). In addition, the incipient roadway-overtopping discharge is analyzed since it has the potential of being the worst-case scour scenario. Total scour at a highway crossing is comprised of three components: 1) long-term streambed degradation; 2) contraction scour (due to accelerated flow caused by a reduction in flow area at a bridge) and; 3) local scour (caused by accelerated flow around piers and abutments). Total scour is the sum of the three components. Equations are available to compute depths for contraction and local scour and a summary of the results of these computations follows.
Contraction scour for all modelled discharges was zero. Left abutment scour ranged from 6.8 to 21.2 ft. Right abutment scour ranged from 13.9 to 18.4 ft. The worst-case abutment scour occurred at the 500-year discharge at the left and right abutments. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution.
It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1995, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.
2
3
Figure 1. Location of study area on USGS 1:24,000 scale map.
Plymouth, VT. Quadrangle, 1:24,000, 1966
Photoinspected 1983
NORTH
4
Figure 2. Location of study area on Vermont Agency of Transportation town highway map.
Figure 3. Structure ROCHTH00210034 viewed from upstream (July 23, 1996).
Figure 6. Structure ROCHTH00210034 viewed from downstream (July 23, 1996).
6
LEVEL II SUMMARY
Structure Number Stream
County
Bridge length
Alignment of bri
Abutment type
Stone fill on abut
Is bridge skewed
Debris accumul
Level I
Potential fo
ROCHTH00210034
7
Road
Description of Bridge
ft Bridge width
ght)
Embankme
ment?
to flood flow according t rvey?
ation on bridge at time of Level I or Level
D Percent blocked
r debris
White River
District
Windsor TH21
nt type
Angle
II site visit:
Percent blocked
4
72
16 70 ft Max span length ft
Straight
dge to road (on curve or strai
Vertical, concrete
Sloping
No
7/23/96
Date of inspection
Type-2, around the upstream end of the upstream left wingwall which
Description of stone fillis slumped. Type-3, around the downstream end of the downstream left wingwall.
Abutments and wingwalls are concrete. Footings are
Brief description of piers/abutments exposed on the downstream end of the upstream left wingwall, left abutment, and upstream end of
the downstream left wingwall.
Y
15
o Level I suN
Is bridge located on a bend in channel? If so, describe (mild, moderate, severe)
ate of inspection 7/23/96
of channel horizontally 0
of channel vertically
0
7/23/96
0 0
Low. There is some debris caught on the vegetation along upstream
Level II
left and right banks.
None. 7/23/96
Describe any features near or at the bridge that may affect flow (include observation date).
Description of the Geomorphic Setting
General topography
Geomorphic conditio
Date of insp
DS left:
DS right:
US left:
US right:
Average top width
Predominant bed ma
Vegetative c
DS left:
DS right:
US left:
US right:
The channel is located within a narrow, flat to slightly irregular flood
plain with moderately sloped valley walls.
wnstream (DS), upstream (US)
ns at bridge site: do
7/23/96
ection
Steep channel bank to a narrow flood plain.
Shallow sloped narrow flood plain.
Narrow flood plain.
Narrow flood plain with a shallow sloped overbank.
Description of the Channel
teri
102
Average depth
al Bank material
8
5
ft
Gravel / Cobbles
ft
Sand/Cobbles
Sinuous but stable
Stream type (straight, meandering, braided, swampy, channelized) with alluvial channel boundaries and a narrow flood plain.
7/23/96
over on channel banks near bridge: Date of inspection Brush and the Village of Rochester.
Pasture with brush
Brush and the Village of Rochester.
Pasture and brush.
Y
? If not, describe location and type of instability and -
Do banks appear stable
date of observation.
None. 7/23/96
Describe any obstructions in channel and date of observation.
Hydrology
Drainage area i2
Percentage of dra
Is drainage a
Is there a USGS
Is there a lake/
Q
m74.8
inage area in physiographic provinces: (approximate)
Perc age area
Physiographic province/section New England/Green Mountain
gage on the stream of interest
USGS gage description
USGS gage number
Gage drainage area mi2
Calculated Discharges
100 ft3/s
9
ent of drain100
Rural
rea considered rural or urban? Describe any significantThe drainage is rural, however the bridge itself is located in the Village of
urbanization: Rochester..
Yes
?
White River near Bethel, VT.
01142000 - discontinued
241
No
pond that will significantly affect hydrology/hydraulics?-
If so, describe
14,830
21,960
Q500 ft3/sThe 100- and 500-year discharges are based on a
Method used to determine discharges drainage area relationship [(74.8/65)exp 0.7] with Flood Insurance Study discharge values at the
upstream corporate limits of Rochester (Federal Emergency Management Agency, 1991). The
drainage area at the upstream corporate limits of Rochester is 65 square miles. The values
computed are within a range defined by several empirical flood frequency curves (Benson,
1962; Johnson and Tasker, 1974; FHWA, 1983; Potter, 1957a&b; Talbot, 1887).
Description of the Water-Surface Profile Model (WSPRO) Analysis
Datum for WSPRO analysis (USGS survey, sea level, VTAOT plans)
Datum tie between USGS survey and VTAOT plans
Cross-Sections Used in WSPRO Analysis
1 For location of cross-sections see plan-view sketch included with Level I field form, Appendix For more detail on how cross-sections were developed see WSPRO input file.
10
1Cross-section
Section Reference Distance
(SRD) in feet
2Cross-section development
EXITX -70 1 Ex
FULLV 0 2DoseEX
BRIDG 0 1 Br
RDWAY 11 1 Ro
APTEM 82 1Apsutem
APPRO 89 2Msefro
USGS survey
None
RM1 is a chiseled X on
Description of reference marks used to determine USGS datum.
top of the upstream end of the right abutment (elev. 496.40 ft, arbitrary survey datum). RM2 is a
chiseled X on top of the downstream end of the left abutment (elev. 496.51 ft, arbitrary survey
datum).
E.
Comments
it section
wnstream Full-valley ction (Templated from ITX)
idge section
ad Grade section
proach section as rveyed (Used as a
plate)
odelled Approach ction (Templated m APTEM)
Data and Assumptions Used in WSPRO Model
11
Hydraulic analyses of the reach were done by use of the Federal Highway
Administration’s WSPRO step-backwater computer program (Shearman and others, 1986, and
Shearman, 1990). The analyses reported herein reflect conditions existing at the site at the time
of the study. Furthermore, in the development of the model it was necessary to assume no
accumulation of debris or ice at the site. Results of the hydraulic model are presented in the
Bridge Hydraulic Summary, Appendix B, and figure 7.
Channel roughness factors (Manning’s “n”) used in the hydraulic model were estimated
using field inspections at each cross section following the general guidelines described by
Arcement and Schneider (1989). Final adjustments to the values were made during the
modelling of the reach. Channel “n” values for the reach ranged from 0.035 to 0.045, and
overbank “n” values ranged from 0.045 to 0.055.
Normal depth at the exit section (EXITX) was assumed as the starting water surface.
This depth was computed by use of the slope-conveyance method outlined in the user’s manual
for WSPRO (Shearman, 1990). The slope used was 0.0020 ft/ft which was estimated from the
100-year water-surface slope downstream of the bridge in the Flood Insurance Study for
The surveyed approach section (APTEM) was moved along the approach channel slope
(0.0014 ft/ft) to establish the modelled approach section (APPRO), one bridge length upstream
of the upstream face as recommended by Shearman and others (1986). This location also
provides a consistent method for determining scour variables.
Bridge Hydraulics Summary
Average bridge embankment eleva ftAverage low steel elevation
100-year discharge Water-surface elevati
Road overtopping? _
Area of flow in bridge openAverage velocity in bridge oMaximum WSPRO tube vel Water-surface elevation at AWater-surface elevation at AAmount of backwater cause
500-year discharge Water-surface elevatio
Road overtopping? __
Area of flow in bridge openAverage velocity in bridge oMaximum WSPRO tube vel Water-surface elevation at AWater-surface elevation at AAmount of backwater cause
Incipient overtopping dischWater-surface elevation in b
Area of flow in bridge openAverage velocity in bridge oMaximum WSPRO tube vel Water-surface elevation at AWater-surface elevation at AAmount of backwater cause
500.6
ft
tion
496.7
ft3/s
14,830
12
ening
ing pening ocity at bridge
pproach section wipproach section wd by bridge
ft3/s ening
ing pening ocity at bridge pproach section wipproach section
d by bridge
arge ridge opening
ing pening ocity at bridge pproach section wipproach sectio
d by bridge
ft496.7
r road _ /s
on in bridge op
_______ DY
2
th bridge
r road _2
th bridge
3
th bridge
_______ ft39,460
ischarge ove
ft722
7.2
ft/s ft/s8.4
ge
dge
/s
dge
ft498.8
ft497.9
ithout brid ft0.9
21,960
ft496.7
/s
n in bridge op
______ DY
_______ ft317,200 ischarge ove
f722
t ft6.9 /s
ft/s8.1
ft500.2
ft499.3
without bri ft0.9
f2,950
t /s ft493.5
f508
t2
f5.8
t/s ft7.0
ft493.9
ft493.9
n without bri ft0.0
Scour Analysis Summary
Special Conditions or Assumptions Made in Scour Analysis
13
Scour depths were computed using the general guidelines described in Hydraulic
Engineering Circular 18 (Richardson and others, 1995). Scour depths were calculated
assuming an infinite depth of erosive material and a homogeneous particle-size distribution.
The results of the scour analysis are presented in tables 1 and 2 and a graph of the scour
depths is presented in figure 8.
Contraction scour for the incipient roadway-overtopping discharge was computed
by use of the Laursen clear-water contraction scour equation (Richardson and others, 1995,
p. 32, equation 20). At this site, the 100-year and 500-year discharges resulted in submerged
orifice flow. Contraction scour at bridges with orifice flow is best estimated by use of the
Chang pressure-flow scour equation (oral communication, J. Sterling Jones, October 4,
1996). Hence, contraction scour for these discharges was computed by use of the Chang
equation (Richardson and others, 1995, p. 145-146).
For the discharges resulting in orifice flow, estimates of contraction scour were also
computed by use of the Laursen clear-water contraction scour equation and are presented in
Appendix F. The streambed armoring depths computed suggest that armoring will not limit
the depth of contraction scour.
Abutment scour was computed by use of the Froehlich equation (Richardson and
others, 1995, p. 48, equation 28). Variables for the Froehlich equation include the Froude
number of the flow approaching the embankments, the length of the embankment blocking
flow, and the depth of flow approaching the embankment less any roadway overtopping.
Figure 7. Water-surface profiles for the 100- and 500-yr discharges at structure ROCHTH00210034 on Town Highway 21, crossing the White River, Rochester, Vermont.
ELE
VA
TIO
N A
BO
VE
AR
BIT
RA
RY
DA
TU
M,
IN F
EE
T
CHANNEL DISTANCE FROM DOWNSTREAM TO UPSTREAM, IN FEET
Figure 8. Scour elevations for the 100-yr and 500-yr discharges at structure ROCHTH00210034 on Town Highway 21, crossing the White River, Rochester, Vermont.
ELE
VA
TIO
N A
BO
VE
AR
BIT
RA
RY
DA
TU
M,
IN F
EE
T
STATIONING FROM LEFT TO RIGHT ALONG BRIDGE SECTION, IN FEET
0 5 10 15 20 25 30 35 40 45 50 55 60 65462
504
462
464
466
468
470
472
474
476
478
480
482
484
486
488
490
492
494
496
498
500
502
100-YR TOTAL SCOUR DEPTHS
500-YR TOTAL SCOUR DEPTHS
ANG
LE O
F R
EPOSE E
XAGG
ERATE
D
UNKNOWNFOUNDATION
UNKNOWNFOUNDATION
100-YEAR WATER SURFACE
500-YEAR WATER SURFACETOP OF DECK
LOW STEEL
17
Table 1. Remaining footing/pile depth at abutments for the 100-year discharge at structure ROCHTH00210034 on Town Highway 21, crossing the White River, Rochester, Vermont.[VTAOT, Vermont Agency of Transportation; --,no data]
Description Station1
1.Measured along the face of the most constricting side of the bridge.
Table 2. Remaining footing/pile depth at abutments for the 500-year discharge at structure ROCHTH00210034 on Town Highway 21, crossing the White River, Rochester, Vermont.[VTAOT, Vermont Agency of Transportation; --, no data]
Description Station1
1.Measured along the face of the most constricting side of the bridge.
Arcement, G.J., Jr., and Schneider, V.R., 1989, Guide for selecting Manning’s roughness coefficients for natural channels and flood plains: U.S. Geological Survey Water-Supply Paper 2339, 38 p.
Barnes, H.H., Jr., 1967, Roughness characteristics of natural channels: U.S. Geological Survey Water-Supply Paper 1849, 213 p.
Benson, M. A., 1962, Factors Influencing the Occurrence of Floods in a Humid Region of Diverse Terrain: U.S. Geological Survey Water-Supply Paper 1580-B, 64 p.
Brown, S.A. and Clyde, E.S., 1989, Design of riprap revetment: Federal Highway Administration Hydraulic Engineering Circular No. 11, Publication FHWA-IP-89-016, 156 p.
Federal Highway Administration, 1983, Runoff estimates for small watersheds and development of sound design: Federal Highway Administration Report FHWA-RD-77-158.
Federal Highway Administration, 1993, Stream Stability and Scour at Highway Bridges: Participant Workbook: Federal Highway Administration Report FHWA-HI-91-011.
Federal Emergency Management Agency, 1991, Flood Insurance Study, Town of Rochester, Windsor County, Vermont: Washington, D.C., August 5, 1991.
Froehlich, D.C., 1989, Local scour at bridge abutments in Ports, M.A., ed., Hydraulic Engineering--Proceedings of the 1989 National Conference on Hydraulic Engineering: New York, American Society of Civil Engineers, p. 13-18.
Hayes, D.C.,1993, Site selection and collection of bridge-scour data in Delaware, Maryland, and Virginia: U.S. Geological Survey Water-Resources Investigation Report 93-4017, 23 p.
Interagency Advisory Committee on Water Data, 1982, Guidelines for determining flood flow frequency: U.S. Geological Survey, Bulletin 17B of the Hydrology Subcommittee, 190 p.
Johnson, C.G. and Tasker, G.D.,1974, Progress report on flood magnitude and frequency of Vermont streams: U.S. Geological Survey Open-File Report 74-130, 37 p.
Lagasse, P.F., Schall, J.D., Johnson, F., Richardson, E.V., Chang, F., 1995, Stream Stability at Highway Structures: Federal Highway Administration Hydraulic Engineering Circular No. 20, Publication FHWA-IP-90-014, 144 p.
Laursen, E.M., 1960, Scour at bridge crossings: Journal of the Hydraulics Division, American Society of Civil Engineers, v. 86, no. HY2, p. 39-53.
Potter, W. D., 1957a, Peak rates of runoff in the Adirondack, White Mountains, and Maine woods area, Bureau of Public Roads
Potter, W. D., 1957b, Peak rates of runoff in the New England Hill and Lowland area, Bureau of Public Roads
Richardson, E.V. and Davis, S.R., 1995, Evaluating scour at bridges: Federal Highway Administration Hydraulic Engineering Circular No. 18, Publication FHWA-IP-90-017, 204 p.
Richardson, E.V., Simons, D.B., and Julien, P.Y., 1990, Highways in the river environment: Federal Highway Administration Publication FHWA-HI-90-016.
Ritter, D.F., 1984, Process Geomorphology: W.C. Brown Co., Debuque, Iowa, 603 p.
Shearman, J.O., 1990, User’s manual for WSPRO--a computer model for water surface profile computations: Federal Highway Administration Publication FHWA-IP-89-027, 187 p.
Shearman, J.O., Kirby, W.H., Schneider, V.R., and Flippo, H.N., 1986, Bridge waterways analysis model; research report: Federal Highway Administration Publication FHWA-RD-86-108, 112 p.
Talbot, A.N., 1887, The determination of water-way for bridges and culverts.
U.S. Department of Transportation, 1993, Stream stability and scour at highway bridges, Participant Workbook: Federal Highway Administration Publication FHWA HI-91-011.
U.S. Geological Survey, 1970, Hancock, Vermont 7.5 Minute Series quadrangle map: U.S. Geological Survey Topographic Maps, Scale 1:24,000.
U.S. Geological Survey, 1970, Rochester, Vermont 7.5 Minute Series quadrangle map: U.S. Geological Survey Topographic Maps, Scale 1:24,000.
U.S. Geological Survey WSPRO Input File roch034.wsp Hydraulic analysis for structure ROCHTH00210034 Date: 8-May-97 Town Highway 21, WHITE RIVER, ROCHESTER, VERMONT ECW *** RUN DATE & TIME: 05-21-97 15:00
U.S. Geological Survey WSPRO Input File roch034.wsp Hydraulic analysis for structure ROCHTH00210034 Date: 8-May-97 Town Highway 21, WHITE RIVER, ROCHESTER, VERMONT ECW *** RUN DATE & TIME: 05-21-97 15:00
U.S. Geological Survey WSPRO Input File roch034.wsp Hydraulic analysis for structure ROCHTH00210034 Date: 8-May-97 Town Highway 21, WHITE RIVER, ROCHESTER, VERMONT ECW *** RUN DATE & TIME: 05-21-97 15:00
XSID:CODE SRDL LEW AREA VHD HF EGL CRWS Q WSEL SRD FLEN REW K ALPH HO ERR FR# VEL
U.S. Geological Survey WSPRO Input File roch034.wsp Hydraulic analysis for structure ROCHTH00210034 Date: 8-May-97 Town Highway 21, WHITE RIVER, ROCHESTER, VERMONT ECW *** RUN DATE & TIME: 05-21-97 15:00
XSID:CODE SRDL LEW AREA VHD HF EGL CRWS Q WSEL SRD FLEN REW K ALPH HO ERR FR# VEL
U.S. Geological Survey WSPRO Input File roch034.wsp Hydraulic analysis for structure ROCHTH00210034 Date: 8-May-97 Town Highway 21, WHITE RIVER, ROCHESTER, VERMONT ECW *** RUN DATE & TIME: 11-07-97 09:03
XSID:CODE SRDL LEW AREA VHD HF EGL CRWS Q WSEL SRD FLEN REW K ALPH HO ERR FR# VEL
United States Geological SurveyBridge Historical Data Collection and Processing Form
Gener
Data collected by (First Initial, Full last name
Date (MM/DD/YY) _
Highway District Number (I - 2; nn)
Town (FIPS place code; I - 4; nnnnn)
Waterway (I - 6)
Route Number
Latitude (I - 16; nnnn.n
Select
Maintenance responsibility (I - 21; nn) _
Year built (I - 27; YYYY)
Average daily traffic, ADT (I - 29; nnnnnn
Year of ADT (I - 30; YY) _
Opening skew to Roadway (I - 34; nn) _
Operational status (I - 41; X) _
Structure type (I - 43; nnn)
Approach span structure type (I - 44; nnn
Number of spans (I - 45; nnn)
Number of approach spans (I - 46; nnnn)
U.S
.DE
PA
RTM N OF H
I
G LC SUV
YET T E
NTERORI
E
OA RI
OL
GE Structure Number
______________ROCHTH00210034
al Location Descriptive
)
F
)
__. _E B
ed
________________OEHMLER
___ /03
____ /22 ____95
County (FIPS county code; I - 3; nnn) _
____04
Vicinity (I - 9)
Road Name (I - 7):
Hydrologic Unit Code:
Longitude (i - 17; nnnnn.n)
eral Inventory Codes
Mile marker (I - 11; nnn.nnn)
_
Maximum span length (I - 48; nnnn
Structure length (I - 49; nnnnnn
Deck Width (I - 52; nn.n)
Channel & Protection (I - 61; n)
Waterway adequacy (I - 71; n)
Underwater Inspection Frequency (I - 92B;
Year Reconstructed (I - 106)
Clear span (nnn.n ft) _
Vertical clearance from streambed (nnn.n f
Waterway of full opening (nnn.n ft2)
31
______027
______60100
_______000000
_____________________________WHITE RIVER
_____________________-
_______TH021
________________________AT JCT TH 52 + TH 21
_________________________Hancock
_________01080105
) _______43527
_______72484
________________10141500341415
_____03
______1927
) _______000060
____91
_____00
XYY)
_____A
______302
______000
t)
_____001
______0000
) _____0070
) ______000072
______160
____6
____7
______N
_______0000
_____-
_____
______
Comments:The structural inspection report of 7/2/93 indicates the structure is a single span steel stringer type bridge with a concrete deck. The abutments are concrete with minor cracks and spalls noted. The footing of the right abutment is not exposed, but the left one is exposed and has some minor spalling near the centerline of the roadway and at the upstream end of the footing. The adjacent streambed is up to 2 feet below the top of the left abutment footing but there is no apparent undermining reported. The streambed consists of mainly stone and gravel. There is a shallow gravel point bar present along the right abutment. Channel scour is noted as minor, if any. The report indicates there is no bank erosion or debris (Cont., page 33)
ge Hydrologic DataIs there hydrologic 2
Terrain character:
Stream character & type
Streambed material:
Discharge Data (cfs): Q2.33
Q50 _
Record flood date (MM / DD
Estimated Discharge (cfs):
Ice conditions (Heavy, Moderate, Light
The stage increases to maximum h
The stream response is (Flashy, Not
Watershed storage area (in perc
The watershed storage area is:
Descrstage:
Water Surface Elevation Estimates
Peak discharge frequency
Water surface elevation (ft))
Velocity (ft / sec)
Long term stream bed changes:
Is the roadway over w t
Relief Elevation (ft):
Are there other structures
Upstream dist
Highway No. :
Clear span (ft): Clear Heig
Brid ____ iN
_____ Q10 __ ____ Q25 _
__ Q100 _ ____ Q500
urfac n (ft):
t Q ft/s): _
) Debris (Heavy, Moderate
ighwat , Not rapidly):
flashy):
(1-mainly at the headwaters; 2- uniformly distributed; 3-imm
for Existing Structure:
Q Q Q Q Q
he Q100? (Yes, No, Unknown): _ Fr
Discharge over roadway at Q100 (ft3/ sec):
Yes, No, Unkno
____ Town:
ht (ft): Full Waterway (ft2):
Structure No. : tructure T
type ctrl-n o
oi the site)
32
_______-
data available? f No, type ctrl-n h VTAOT Drainage area (mi ):
Impact Severity: 0- none to very slight; 1- Slight;
37
Bridge wi
____ /07
Overat; 7- W
lindrica
ge (B
or N)
e
or N)
e
skew
ngle
2- Mod
dth
____ / 23
letland)
l culvert;
F):
Q
Ope
erate; 3-
fee
to
9____96
itial, Fu
_____04
Date (MM/DD
r ______________000000
ay District Number
y___________________________027
______________________________
marke
ROCHESTER 60100
_________________________________WHITE RIVER
__________________________- 6)
r ________TH 021
: ___________01080105
3. Descriptive comments:Single span, steel stringer bridge with a concrete deck and asphalt overlay. Bridge is located at junction with TH52 and TH51.
_____2
_____4 _____2 _____4 l _____4 uburban
______2
_____
w crops;2
asture; 5
_____ (2
ce...
e _____( 16
1
t)
________ (72 ________ (70 ______ (16
____ R1
____1
____ R1
____ (1
ning skew
.Type
_____1
.Cond.
_____3
_____1 _____2
_____0
_____- _____0 _____-
_____0
_____- _____0 _____-
_____1
_____2 _____0 _____-
_____10
: _____15
_____ (Y
l impact
_____ (LB
Y
____1
? _____ f30
t ____ (US _____fe0 t ____DS
_____ (N
_____ (
Y
____
_____ f
t ____(U _____fe t ____
t ________
kment slope
1.3:1
t _______
in feet / foot)
1.5:1
=
roadway
0.0
: _______ DEW
: __________9/27/96
: _______ DEW
: __________9/27/96
_______ DEW
: __________6/4/97
Severe
C. Upstream Channel Assessment
21. Bank height (BF) 22. Bank angle (BF) 26. % Veg. cover (BF) 27. Bank material (BF) 28. Bank erosion (BF)
18. Bridge Type
1a- Vertical abutments with wingwalls
1b- Vertical abutments without wingwalls
2- Vertical abutments and wingwalls, sloping embankmentWingwalls perpendicular to abut. face
3- Spill through abutments
4- Sloping embankment, vertical wingwalls and abutmentsWingwall angle less than 90
1b without wingwalls1a with wingwalls
2
3
4
19. Bridge Deck Comments (surface cover variations, measured bridge and span lengths, bridge type variations,
_______
20. SRD
66.0
Bed and
Bank Ero
23. Bank w
30 .Bank p
Bank pro
Bank pro
SRD - Se
LB RB
_____
LB
_____ _____ _ 4.5
bank Material: 0- organics; 1-
sion: 0- not evident; 1- light flu
idth 24. Cha
4- cobble, 64 -
rotection type: LB
tection types: 0- absent; 1- < 1
tection conditions: 1- good; 2-
ction ref. dist. to US face
RB
____ 6.0
nnel width 25. Thalweg dept 29. Bed Materia
_____ 20.0
% Vegesilt / clay,
vial; 2- m256mm; 5
RB
2 inches;
slumped;
_____ 15.0
tation (Veg) cover: 1- 0 to 25%; 2- 26 < 1/16mm; 2- sand, 1/16 - 2mm; 3- g
oderate fluvial; 3- heavy fluvial / mas- boulder, > 256mm; 6- bedrock; 7- m
31. Bank protection c
2- < 36 inches; 3- < 48 inches; 4- < 6
3- eroded; 4- failed
38
h _____ 109.5
: ______4
approach overflow width, etc.)
#4: A horse farm exists on the upstream and downstream right overbanks beyond bank trees and paved road, as indicated in plan view sketch. A Department of Public Works facility exists on the downstream left over-bank. The upstream left overbank is lawn with an old industrial building.
LB
_____2
RB
_____4
LB
_____432
to 50ravel
s wasanm
ondit
0 inc
RB
_____234
%; 3- 51 to 7, 2 - 64mm;
tingade
ion: LB
hes; 5- wall
LB
_____2
5%; 4- 76 to
RB
/ artificial lev
RB
_____1
l _____432
_____1
_____0 _____3 _____-
100%
ee
32. Comments (bank material variation, minor inflows, protection extent, etc.):#29: The bed material is larger along the left bank and in the scour hole from the cross-section to under the bridge
#30: Left bank protection extends from 28 feet upstream to the end of the wingwall at 8 feet upstream. The protection is stone fill.
47. Scour dimensions: Length idth epth
46. Mid-scour distance
49. Are there major c ces? o ctrl-n mc) 50. Ho
51. Confluence 1: Distance 52. Enters o B or RB) 53. Typ 1- perennial; 2- ephemeral)
Confluence 2: Distance Enters on LB or RB) Type ( 1- perennial; 2- ephemeral)
38. Point or side bar comments (Circle Point or Side; Note additional bars, material variation, status, etc.):There is an additional point bar from 250 feet upstream to 195 feet upstream. It is composed of cobble and gravel with some grass. The mid-bank is 215 feet upstream where it is 25 feet wide. The point bar is posi-tioned 0% LB to 20% RB.
_____ (Y
_____ (LB presen: _____130
cb)
: _____ fe158
t ____ (UUS re?
o _____ fe112
LB or RB
t ____ (UUS
ance
: _____ 1
44. Cut bank comments (eg. additional cut banks, protection condition, etc.):The cut-bank is protected by eroded type 2 protection, dumped concrete pieces.
There is an additional cut-bank extending from 360 feet upstream to 265 feet upstream. It is presently erod-ing via eddying; at bank full, the bank will be directly impacted.
_____ (Y
: _____130
______ W90
______ D20 : _____2 ____ %0 _____ %25 48. Scour comments (eg. additional scour areas, local scouring process, etc.):Scour depth is based on thalweg of 2.0 feet.A second scour hole, 1.5 feet, extends from 30 feet upstream to 35 feet downstream. Mid-scour is at the down-stream bridge face. There is third scour hole with a mid-scour distance located 200 feet upstream. It is 60 feet long, 30 feet wide and 2 feet deep based on a thalweg of 2 feet.
Comments (eg. bank material variation, minor inflows, protection extent, etc.):
2434223411432202-The left bank protection extends from the downstream end of the downstream left wingwall (10 feet down-stream) to 25 feet downstream. There is also type 1 protection from 160 feet downstream to 550 feet down-
____ (str
type ct
l: ____ (ea
105. Drop structure comments (eg. downstream scour depth):m.
Scour dimensions: Length id
Is channel scour p
Are there major c cesConfluence 1: Distance
Confluence 2: Distance
106. Point/Side bar present? Y or N. if N type ctrl-n pb) Mid-bar widthMid-bar distance:
Point ba ee S
Point or side bar comments (Circle Poi
Material:
Is a cut-banCut bank exte e S,
Bank damage ( 1- eroded and/
F.
107. Stage of reach evolut
_____ (
th epth
Mid-scourY or if N typ s)
Positioned
? Y or ctrl-n mc) How
Enters o LB or RB) Typ
Enters o LB or RB) Typ
43
, UB, DS) to e S, UB, DS) posit
nt or Side; note additional bars, material variation, s
Y or if N t c re? LB or RB
UB, DS) t e S, UB, DS)
or creep; 2- slip failure; 3- block failure)
Geomorphic Channel Assessmen
ion _ 1- Constructed2- Stable3- Aggraded4- Degraded5- Laterally unstable6- Vertically and laterally u
______
LB to RB
1- perennial; 2- eph
1- perennial; 2- eph
ioned LB to
tatus, etc.):
) Mid-bank distance
t
nstable
: ______
RB
: ______ f t ____ (U ______ fe t ____ (U ____ %N _____ %- r extent
_____NO
DROP STRUCTURE
_____ (
_____ ( : _____N k preset: _____ fe-
nt?
t ____ (U-
ype ctrl-n
o _____ fe-
b) Whe
t ____ (U-
n
: _____ -
Cut bank comments (eg. additional cut banks, protection condition, etc.):----
_____ (NO
: _______POIN
______ W
resent?T
______ DBAR : _____
e ctrl-n c
S
distance
____ %
____ %
Scour comments (eg. additional scour areas, local scouring process, etc.):
YLB120
_____ (95
_____DS
emeral)
onfluen _____130
if N type
_____ (DS
many?
e _____ (1
emeral)
_____
n
n _____ (
e _____ (
Confluence comments (eg. confluence name):
Y
____0
108. Evolution comments (Channel evolution not considering bridge effects; See HEC-20, Figure 1 for geomorphic
descriptors):DS77151.52045This scour hole was also mentioned in the upstream channel assessment.
N--
44
109. G. Plan View Sketch
45
point bar
cut-bank
scour hole ambient channelrip rap or
debris stone wall
other wallflow
cross-section
pb
cb
Q
stone fill
-
-
46
APPENDIX F:
SCOUR COMPUTATIONS
SCOUR COMPUTATIONS Structure Number: ROCHTH00210034 Town: ROCHESTER Road Number: TH 21 County: WINDSOR Stream: WHITE RIVER Initials ECW Date: 5/2/97 Checked: SAO Analysis of contraction scour, live-bed or clear water? Critical Velocity of Bed Material (converted to English units) Vc=11.21*y1^0.1667*D50^0.33 with Ss=2.65 (Richardson and others, 1995, p. 28, eq. 16) Approach Section Characteristic 100 yr 500 yr other Q Total discharge, cfs 14830 21960 2950 Main Channel Area, ft2 1214 1367 680 Left overbank area, ft2 489 683 80 Right overbank area, ft2 1151 1928 4 Top width main channel, ft 109 109 109 Top width L overbank, ft 118 159 66 Top width R overbank, ft 512 583 22 D50 of channel, ft 0.244 0.244 0.244 D50 left overbank, ft -- -- -- D50 right overbank, ft -- -- -- y1, average depth, MC, ft 11.1 12.5 6.2 y1, average depth, LOB, ft 4.1 4.3 1.2 y1, average depth, ROB, ft 2.2 3.3 0.2 Total conveyance, approach 296918 431059 77659 Conveyance, main channel 197428 240681 75128 Conveyance, LOB 34012 48745 2481 Conveyance, ROB 65478 141633 49 Percent discrepancy, conveyance 0.0000 0.0000 0.0013 Qm, discharge, MC, cfs 9860.8 12261.3 2853.9 Ql, discharge, LOB, cfs 1698.8 2483.3 94.2 Qr, discharge, ROB, cfs 3270.4 7215.4 1.9 Vm, mean velocity MC, ft/s 8.1 9.0 4.2 Vl, mean velocity, LOB, ft/s 3.5 3.6 1.2 Vr, mean velocity, ROB, ft/s 2.8 3.7 0.5 Vc-m, crit. velocity, MC, ft/s 10.5 10.7 9.5 Vc-l, crit. velocity, LOB, ft/s ERR ERR ERR Vc-r, crit. velocity, ROB, ft/s ERR ERR ERR Results Live-bed(1) or Clear-Water(0) Contraction Scour? Main Channel 0 0 0 Left Overbank N/A N/A N/A Right Overbank N/A N/A N/A
47
Clear Water Contraction Scour in MAIN CHANNEL y2 = (Q2^2/(131*Dm^(2/3)*W2^2))^(3/7) Converted to English Units ys=y2-y_bridge (Richardson and others, 1995, p. 32, eq. 20, 20a) Bridge Section Q100 Q500 Other Q (Q) total discharge, cfs 14830 21960 2950 (Q) discharge thru bridge, cfs 5211 4988 2950 Main channel conveyance 87258 87258 75967 Total conveyance 87258 87258 75967 Q2, bridge MC discharge,cfs 5211 4988 2950 Main channel area, ft2 722 722 508 Main channel width (normal), ft 67.0 67.0 66.2 Cum. width of piers in MC, ft 0.0 0.0 0.0 W, adjusted width, ft 67 67 66.2 y_bridge (avg. depth at br.), ft 10.78 10.78 7.67 Dm, median (1.25*D50), ft 0.305 0.305 0.305 y2, depth in contraction,ft 7.26 6.99 4.50 ys, scour depth (y2-ybridge), ft -3.52 -3.79 -3.17
Armoring Dc=[(1.94*V^2)/(5.75*log(12.27*y/D90))^2]/[0.03*(165-62.4)] Depth to Armoring=3*(1/Pc-1) (Federal Highway Administration, 1993) Downstream bridge face property 100-yr 500-yr Other Q Q, discharge thru bridge MC, cfs 5211 4988 2950 Main channel area (DS), ft2 722 722 508 Main channel width (normal), ft 67.0 67 66.2 Cum. width of piers, ft 0.0 0.0 0.0 Adj. main channel width, ft 67.0 67.0 66.2 D90, ft 0.5179 0.5179 0.5179 D95, ft 0.5674 0.5674 0.5674 Dc, critical grain size, ft 0.1714 0.1570 0.1259 Pc, Decimal percent coarser than Dc 0.662 0.702 0.781 Depth to armoring, ft 0.26 0.20 0.11
48
Pressure Flow Scour (contraction scour for orifice flow conditions) Chang pressure flow equation Hb+Ys=Cq*qbr/Vc Cq=1/Cf*Cc Cf=1.5*Fr^0.43 (<=1) Cc=SQRT[0.10(Hb/(ya-w)-0.56)]+0.79 (<=1) Umbrell pressure flow equation (Hb+Ys)/ya=1.1021*[(1-w/ya)*(Va/Vc)]^0.6031 (Richardson and other, 1995, p. 144-146) Q100 Q500 OtherQ Q, total, cfs 14830 21960 2950 Q, thru bridge MC, cfs 5211 4988 2950 Vc, critical velocity, ft/s 10.47 10.68 9.50 Va, velocity MC approach, ft/s 8.12 8.97 4.20 Main channel width (normal), ft 67.0 67.0 66.2 Cum. width of piers in MC, ft 0.0 0.0 0.0 W, adjusted width, ft 67.0 67.0 66.2 qbr, unit discharge, ft2/s 77.8 74.4 44.6 Area of full opening, ft2 722.0 722.0 508.0 Hb, depth of full opening, ft 10.78 10.78 7.67 Fr, Froude number, bridge MC 0.39 0.37 N/A Cf, Fr correction factor (<=1.0) 1.00 0.98 ERR **Area at downstream face, ft2 N/A N/A N/A **Hb, depth at downstream face, ft N/A N/A N/A **Fr, Froude number at DS face ERR ERR ERR **Cf, for downstream face (<=1.0) N/A N/A N/A Elevation of Low Steel, ft 496.67 496.67 496.67 Elevation of Bed, ft 485.89 485.89 489.00 Elevation of Approach, ft 498.82 500.22 N/A Friction loss, approach, ft 0.32 0.41 N/A Elevation of WS immediately US, ft 498.50 499.81 ERR ya, depth immediately US, ft 12.61 13.92 N/A Mean elevation of deck, ft 500.56 500.56 500.56 w, depth of overflow, ft (>=0) 0.00 0.00 N/A Cc, vert contrac correction (<=1.0) 0.96 0.94 ERR **Cc, for downstream face (<=1.0) ERR ERR ERR Ys, scour w/Chang equation, ft -3.05 -3.16 ERR Ys, scour w/Umbrell equation, ft 1.15 3.03 ERR
49
Abutment Scour Froehlich’s Abutment Scour Ys/Y1 = 2.27*K1*K2*(a’/Y1)^0.43*Fr1^0.61+1 (Richardson and others, 1995, p. 48, eq. 28) Left Abutment Right Abutment Characteristic 100 yr Q 500 yr Q Other Q 100 yr Q 500 yr Q Other Q (Qt), total discharge, cfs 14830 21960 2950 14830 21960 2950 a’, abut.length blocking flow, ft 118.3 159.5 66.4 553.9 625.4 64.2 Ae, area of blocked flow ft2 496.5 591 93.1 373.9 632 202.5 Qe, discharge blocked abut.,cfs 1804 -- 135.84 -- -- 674.3 (If using Qtotal_overbank to obtain Ve, leave Qe blank and enter Ve and Fr manually) Ve, (Qe/Ae), ft/s 3.63 3.84 1.46 3.99 4.59 3.33 ya, depth of f/p flow, ft 4.20 3.71 1.40 0.68 1.01 3.15 --Coeff., K1, for abut. type (1.0, verti.; 0.82, verti. w/ wingwall; 0.55, spillthru) K1 0.82 0.82 0.82 0.82 0.82 0.82 --Angle (theta) of embankment (<90 if abut. points DS; >90 if abut. points US) theta 90 90 90 90 90 90 K2 1.00 1.00 1.00 1.00 1.00 1.00 Fr, froude number f/p flow 0.313 0.325 0.217 0.420 0.414 0.330 ys, scour depth, ft 20.35 21.22 6.80 13.93 18.43 14.07 HIRE equation (a’/ya > 25) ys = 4*Fr^0.33*y1*K/0.55 (Richardson and others, 1995, p. 49, eq. 29)
Abutment riprap Sizing Isbash Relationship D50=y*K*Fr^2/(Ss-1) and D50=y*K*(Fr^2)^0.14/(Ss-1) (Richardson and others, 1995, p112, eq. 81,82) Downstream bridge face property Q100 Q500 Other Q Q100 Q500 Other Q Fr, Froude Number 0.39 0.37 0.38 0.39 0.37 0.38 y, depth of flow in bridge, ft 10.78 10.78 7.67 10.78 10.78 7.67 Median Stone Diameter for riprap at: left abutment right abutment, ft Fr<=0.8 (vertical abut.) 1.01 0.91 0.68 1.01 0.91 0.68 Fr>0.8 (vertical abut.) ERR ERR ERR ERR ERR ERR